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CLINICAL TOXICOLOGY, 15(1), pp. 1-11 (1979) The Practice of Medical Toxicology* EBIC & COLiSTOCK,t M.D., A.B.M.T. Department of Medicine Baylor Collect of Medicine Texas 77030 Department of Pharmacology University of Texas Medical School at Houston Houston, Tens 77030 ABSTRACT Two btmdred twelve consecutive cases presenting to a medical toxicologist related to chronic occupational exposure (49%), acute occupational exposure (24%), and nonoceupational ex posure (27%). Chief complaints were respiratory (36%), be havioral (28%), neuropathy (17%), and organic brain syndrome (10%X In 90% of patients, litigation was in process or under consideration. Referrals were from plaintiff attorneys (37%), from employers. Insurance companies, and defense attorneys (26%), and from physicians (24%). Outcome of assessment revealed 55% to be unrelated to toxic substances, 39% probably related, and 6% positively related. "Presented at the 1978 Annual Meeting of the AACT, Chicago. tAddrsss reprint request to 1802, Medical Towers, Houston 77030. 1 ucc 057809 2 COMSTOCK INTRODUCTION Medical toxicology ia a new medical specialty with certification of physician* first offered in 1975. Twenty-six of the 30 physicians certi fied from 1975 through 1977 reside in the United States [1]. In the ab sence of a residency in medical toxicology, most of the diplomates have primary training in other specialty area- such as pediatrics, emergency medicine, or clinical pharmacology, wb.eh they continue to practice pri vately or as faculty or staff in universities or industry. The qualifica tions for the boards specify that after 1984 candidates must have com pleted an approved 2-year residency in medical toxicology. The only residency now Anting in the world was nitiated in 1976 in Montevideo, Uruguay [2], Several centers in the Uni ed States have active interest in developing a residency but no prograj i is likely to be initiated prior to 1980. The professional and economic feasibility of medical toxicology as a single specialty has not yet been demonstrated. It is assumed that increased Interest in the impact of toxic substances on human health will generate positions in industry, governmental agencies, and univer sities for graduates of a medical toxicology residency. Only a few in dividuals in the United States have accumulated experience with a pri vate practice limited completely to medical toxicology. The opening of an office for the practice of medical toxicology in a professional building near the Tegas Medical Center was proceeded by 14 years of full time involvement in clinical toxicology based in labor atory, academic, and clinical research and service institutions. Con sultation on diagnosis and treatment of human illness thought to be re lated to toxic substances was provided as requested. As a part-time private practitioner, 1300 cases were attended of which approximately 900 were admissions to intensive care units for acute poisoning. Pa tient attendance varied from 1 to 96 hours. During the peak hospitalbased practice in 1967, seven patients were attended concurrently as admitting physician in five intensive care units. With the emergence of the full-time emergency physician and the hospital-based intensive care physician, the need for the toxicologist as a primary care practi tioner has decreased and the practice was limited to consultation only. METHODS A retrospective analysis was conducted on the records of 212 con secutive eases presenting in private office for the practice of medi cal toxicology. Except for consultations requested on patients already In the hospi tal, all procedures were performed on an outpatient basis. Patients from out of town generally stayed at a nearby hotel for the 1 to 3 days ucc 057810 THE PRACTICE OF MEDICAL TOXICOLOGY 3 required for clinical evaluation. Toxicologist-patient contact averaged about 3 hour* and included the usual medical evaluation Including com* plete physical and neurological examination. Most patients were in addition administered a brief neuropsychological test battery and an MMPL Special attention was given to occupational history starting with the last year in school. All jobs held and all potent!*' occupa tional exposure to toxic substances were explored. Inqi iry was TMi into food habits, drug use, hobbies, and avocations. Employers were sometimes contacted to further clarify the nature of toxic hazards, al though frequently this was not helpful. When required, additional diag nostic procedures, such as laboratory examinations, EMr, EKG, pul monary functions, and complete Halsted-Reitan neuropsy dtological batteries, were obtained during subsequent days. Copie: of the hospi tal records and reports from previous physicians were eviewed. In quiry was made concerning other individuals who sustained the same or similar exposure. Epidemiologic investigation frequently provides increased certainty to the determination of the etidlogie relationship. Occupational health and industrial hygiene monitoring records were obtained, if possible. Assessment of causal relationship frequently required literature searches using Medline and Toxline data base and manual search of the toxicology library. Recovery of appropriate original publications varied from 1 or 2 to more than SO reprints. A final decision on eti ology sometimes required 3 to 4 weeks depending upon literature availability. Based upon the above data and the clinical experience of the author, the etiologlc role of toxic substances was assigned to one of three categories: boos, probabls, or positive. Caeea where expoenre was clearly Insufficient, where the syndrome Is one not associated with the substances involved, where "<**! manifestations did not occur in an appropriate time frame, or where other disease processes clearly provided a more tenable hypothesis were assigned to "none." Where the clinical syndrome waa one reasonably associated with the alleged substance, where the time frame waa appropriate, where suf ficient dose appeared probable or when multiple cases occurred from the same environment, and where no more reasonable medical cause could be determined, the cases wire assigned to "probable." Although a causation was not proven beyond any doubt, it was more likely than not, permitting these cases to meet the test of reasonable medical probability. Cases were assigned to "positive" when in addition to they conditions tor probable, objective evidence supported overwhelming exposure, environmental monitoring established the preaence of the toxic substance in hazardous quantities, characteristic biochemical changes occurred In the patient and/or the substance, or its deriva tive* were Identified in biological specimens in quantities consistent with potentially hazardous exposure. Some eases clearly meeting the - i t ucc 057811 COMSTOCK .. . f noaitlve" concerning a brief acute intoxication were > cruena u/V-probable" or "none" when the chief complaint was long-term disability with questionable or no relationship totbetaUJal acute episode. RESULTS Referral sources for 212 consecutive cases presenting to a private medical toxicology office are displayed in Table 1. Referral from plaintiff attorney offices accounted for more than one-third. Such cases often are not yet involved in any legal action but are referred for advice to the patient and the attorney concerning probability of relationship. Physician referrals amounted to one-fourth of the cases. Referrals from Insurance companies provided 11.7%. 10.4% were referred by defense attorneys and legal action of some type always was in process. Other patients and self-referral ac counted for 8% All other sources provided 8.4% Source of alleged exposure is presented in Table 2. 73.1% origin ated from the work place, and 10.4% were nonoccupational acute ex posures of which about half were acute hospital care patients. Mis cellaneous circumstances accounted for approximately 13%. "Unknown" Included patients who believed themselves to be poisoned but could not account for route or occasion when poisoning might have occurred. The nature of clinical complaints Is presented in Table 3. Multiple systems frequently were involved, but only major complaints are listed. TABLE L Distribution of 212 Consecutive Cases by Referral Source Source n% Attorney--plaintiff 78 36.7 Physician S3 24.0 Insurance company 25 1L7 Attorney--defense 23 10.4 Patient 17 8.0 Employer 8 4.2 Union 5 2.3 Service organisation 3 L4 Industrial Accident Board 1 0.4 UCC 057812 THE PRACTICE OF MEDICAL TOXICOLOGY 5 TABLE 2. DistrUxition of 212 Consecutive Cases by Type of Exposure Type Occupational chronic Occupational acute Nonoccupailonal acute Drug abuse Adverse drug effect Unknown Noooceupalional chronic Self-inflicted Other n% 104 49.4 90 23.7 22 10.4 9 4.2 7 3.3 7 3.3 6 2.8 5 2.3 2 ao TABLE 3. Presenting Problems la 212 Consecutive Cases2 Organ system n% Respiratory Behavioral Neuropathy Organic brain syndrome Skin Death Cardiovascular Hematopoietic Other Cancer Hepatic Cobbs Trauma Renal 78 36.0 60 2810 36 17.1 21 9l9 17 ao 15 7.1 9 4.2 6 L8 8 as 6 2.8 6 L8 5 as 2 L0 1 as ^Multiple system involvement occurs. ucc 057813 8 COMSTOCK TABLE 4. Geographic Distribution of 212 Consecutive Cases n% Greater Houston Other Texas cities Tyler Beanmont Dallas-Fort Worth Austin Galveston El Paso Victoria IS 9 15 13 2 3 1 1 134 63 - 59 2? Other states Wyoming Alaska Nevada Pennsylvania Xndiuft Arkansas Florida Qliln Utah Massachusetts Total 1 3 1 1 1 2 1 1 1 1 19 212 9 Boms patients had minor complaints involving almost every organ sys tem. The respiratory system was most frequently involved. Behavioral problems excluding organic brain syndrome were very common, with anxiety neurosis with or without depression the most common. Neuro pathies were the third most frequent presentation. Among 212 cases, in 15 the Issue was the cause of death. Geographic distribution is shown in Table 4: 63% originated in the ucc 057814 ) THE PRACTICE OP MEDICAL TOXICOLOGY 7 TABLE & Assessment Outcome by Referral Source for 121 Consecutive Cases Percentage distribution Referral source Attorney--plaintiff Physician Insurance company Attorney--defense. Patient (self) Employer Union Service organisation Industrial Accident Board Total cases: Number 42 28 15 14 9 7 3 2 1 121 None4 45 67 40 64 67 71 33 50 100 55 Probable** 47 25 S3 28 33 28 67 50 Positive6 7 7 6 7 0 0 0 0 00 39 6 aNooe: No toxicologic basis. bProbable: Toxicologic basis confirmed clinically La, reasonable medial probability. cPositive: Toxicologic basis established beyond any reasonable greater Houston area, 27% were referred from other Texas cities, and 8% were from out of state. Assessment outcome is presented in Table 5 for 121 consecutive cases. Etiology was determined to be toxic substances in 45% and un related to toxic substances in 55% The relationship could be considered "positive" in only 6% of the cases. Table 6 displays an inventory of substances alleged to have caused poisoning. This Illustrates the diversity of substances which come under consideration. As Indicated in Table 5, tbe etiologlc role could not be supported In 55% of the cases. DISCUSSION The private practice of medical toxicology involves an adult popula tion almost exclusively. Association of the illness with employment is ucc 057815 TABLE 6. Inventory of Substances Alleged as Causes of Poisoning Substance Number Subtotal % Substance Number Pharmaceuticals 15 7 Alcohol Metals 38 18 Inorganics Aluminum alkyl 2 Ammonia 3 Antimony 1 Asbestos 2 Arsenic 8 Carbon monoxide 2 Chromium 1 Chlorine 2 Lead 15 Duet, inorganic 3 Manganese 1 Fluoride 3 Mercury 5 Hydrogen sulfide 1 Molybdenum 1 Hydrochloric acid 2 Nickel 2 Nitrogen dioxide 1 Titanium 1 8illca 2 Vanadium 1 Sulfur dioxide 2 Pesticides 22 10 Allphatics Chlordane 2 Acetone. 1 DDVP 1 Carbon tetrachloride 1 Diazlnon * 2 Chloramine 1 Dursban 1 Ethyl acrylate 1 Subtotal % 3 1.5 23 11 33 18 COMSTOCK THE PRACTICE OF MEDICAL TOXICOLOGY Dlsyston Leptophos Milathloa Naled Paxathion Propanil Zinc phosphide Aromatics Aniline Benzene Btsphenol D1chlorobenzene Dlnltrochloro- benzene * Polychlorinated biphenyl Pyridine Toluene Toluene diiso cyanate 1 7 2 1 .2 1 2 1 1 3 1 1 1 3 4 5 20 Formaldehyde Hydrazine Phosgene Methyl bromide Methyl ethyl ketone Methylene chloride n-Hemne Perehloroethylene 1,1-Trlchloro- ethane Styrene Vinyl chloride Others Cyclonlte Cyclohexane Organic vapors Unknown substances 1 1 1 1 2 1 8 2 3 2 7 2 1 3 19 36 UCC 057816 L5 9 17 10 COMSTOCK alleged la 75% of the eases. Nbnoccupational personal Injury la al leged In about 15% of the eases. Some type of litigation has been ini tiated or is being considered In 90% of the eases. The major issue to be resolved is causation, while consultation on treatment is less fre quently required. Exposure to toxic substances bad terminated weeks to years prior to examination in n* jet eases. Because exposure usu ally was remote In time, unequivoeable proof of association with toxic substances was rarely possible. Because the outcome of litigation is influenced frequently by the toxicology consultation, the results are almost always scrutinized closely by all parties in the adverse ry system. Rendering an opinion after a brief office consultation is >arely satisfactory. The spectrum of substances involved in a routine office practice is so broad that most cases become miniature die .cal and literature research pro jects before an opinion can be developed, the time invested in each case differs significantly from the usual medical practice, ranging from an hour to as much as 30 hours. The frequency of involvement of the medical toxicologist with med ical legal problems is a reflection of our ehemosynthetle environment. Once the overwhelming majority of toxic substances are products of human manufacture, routes for economic recovery for injuries through tbs judicial system are potentially open- Despite the apparent high liability for requirement of sworn testimony, depositions or court ap- pssrinces occurred on the average of two times per month. As Is common with malpractice casts, potentially toxic exposures become tbs subject of litigation as the result of comments made by physicians which are inappropriate or misunderstood by tbs patient Association of an illness with employment is sometimes made rather Indiscriminately without an understanding of the relationship. Many of the 55% of cases classified as unrelated were precipitated by com ments such aa "those chemicals have eaten away half your lung," "1 would never work out there with ail those poisons," "everyone knows these chemicals cause cancer," or "let me have your spinal cord be cause I'm doing research on whether lead causes your disease." The physician's role In provoking morbidity unrelated to toxic substances has bees discussed [3]. fa contrast, the work-related neuropathies are commonly misdiag nosed as amyotrophic lateral sclerosis1 or multiple sclerosis. The nature of a patient* occupational exposure to toxic substances often is not explored as a routine part of the clinical evaluation. Experience with the private practice of medical toxicology affirms the continuing need to encourage more emphasis on toxicology to the medical curriculum. More general recognition of medical toxi cology is seeded to permit consultation early in the clinical course of so illness. ucc 057817 THE PRACTICE OF MEDICAL TOXICOLOGY REFERENCES 11 [1] H. Redetzki and J. E. Ott, Functions and goals of ths American Board of Medical Toxicology of the America Academy of Clini cal Toxicology, J. Anal. ToxlcoL, 2, 153-l'i4 (1978), (2] E. G. Comstock, G. Fernandez, A. C. Esponda, H. Decedo, and J. Pronczuk de Garbino, Toxicology and clinical toxicology in Uruguay, Submitted to Clinical Toxicology. (31 E. G. Comstock, Morbidity due to non-poiso> ins. J.' Occup. Med., 20, 755-758 (1978). UCC 057818